An example of conventional hologram recorder is disclosed in Patent Document 1. In the hologram recorder disclosed in this document, a signal beam is irradiated perpendicularly to a recording medium, while a reference beam for recording (hereinafter referred to as a “recording reference beam”) is irradiated with various incident angles, which is achieved by controlling the inclination of a multiple mirror. The multiple mirror is held inclined, with a point supported by a support member serving as a fulcrum. The support member is movable in parallel to the recording medium. The recording reference beam is caused to strike the recording medium at various incident angles in accordance with the inclination of the multiple mirror. In this process, the multiple mirror moves in parallel to the recording medium so that the recording reference beam overlaps the signal beam. With this arrangement, due to the interference of the signal beam and the recording reference beam on the recording medium, multiple holograms corresponding to the crossing angle are recorded.
Patent Document 1: Japanese Laid-open Patent Publication No. 2005-234145
In the conventional hologram recorder, however, to change the incident angle of the recording reference beam, the inclination of the multiple mirror needs to be controlled. Further, the amount of parallel movement of the multiple mirror relative to the recording medium also needs to be controlled for preventing the recording reference beam from deviating from the position irradiated with the signal beam. Thus, the control is complicated.
Moreover, the recording reference beam strikes the multiple mirror with a constant beam diameter. Thus, according to the cosine law of illumination, the light intensity on the recording medium decreases as the incident angle at the recording medium increases. Such decrease in the light intensity can be compensated for by increasing the irradiation time in accordance with an increase in the incident angle, which, however, makes the recording time longer.